Melanin is a class of compounds found in plant, animal and protista kingdoms, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole (also known as hydroquinone) and dihydroxyindole carboxylic acid. Another common form of melanin is pheomelanin, a red-brown polymer of benzothiazine units largely responsible for red hair and freckles. Due to the complex nature of melanin, the exact chemical make up of the various types of melanin are still under investigation.
Both pheomelanin and eumelanin are found in human skin and hair, but eumelanin is the most abundant melanin in humans.
Eumelanin polymers have long been thought to comprise numerous cross-linked 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) polymers. However, the precise nature of eumelanin's molecular structure has not been identified. Eumelanin is found in hair and skin, and colors hair grey, black, yellow, and brown.
Pheomelanin is also found in hair and skin and is both in lighter skinned humans and darker skinned humans. In general women have more pheomelanin than men, and thus women's skin is generally redder than men's. Pheomelanin imparts a pink to red hue and, thus, is found in particularly large quantities in red hair.
Melanin is considered an effective radical scavenger.
Deficiencies of melanin can lead to Parkinson's disease, Alzheimer's disease, retinitis pigmentosa, xeroderma pigmentosum, schizophrenia and dementia.
Increased melanin levels can help increase darkening of hair color thus reducing the amount of grey hair associated with aging.
Therefore, a need exists for improved melanin like agents that help to remedy one or more of the above-identified conditions.